Esters of tetrahydroxy dineoalkyl ethers

ABSTRACT

Esters of organic monocarboxylic acids and dineoalkyl ethers with a tetrahydroxy functionality and corresponding to the general structure   WHEREIN EACH R is an alkyl, aryl, or alkyaryl group of one to 12 carbon atoms. These compounds are effective as high performance functional fluids and lubricant base stocks over a wide temperature range.

United States Patent Gash [ ESTERS OF TETRAHYDROXY DINEOALKYL ETHERS[72] Inventor: Virgil W. Gash, Ballwin, Mo.

[73] Assignee: Monsanto Company, St. Louis, Mo.

[22] Filed: June 12, 1969 [21] Appl. No.: 832,842

[52] U.S. Cl ..260/488 J, 252/56 S, 252/57, 260/4l0.5, 260/410.6,260/468 R, 260/476 R, 260/488 CD [51] Int. Cl ..Cllc 3/08 [58] Field ofSearch ..260/41.0.6, 488 1,488 CD,410.5

[56] References Cited UNITED STATES PATENTS 2,991,297 7/1961 Cooley eta1 ..260/488 3,282,971 11/1966 Metro et al. ..260/4l0.6 3,328,427 6/1967Melaas ..260/4l0.6 3,564,044 2/1971 Chao et a1 ..260/488 51 .Aug. 1,1972 [5 7] ABSTRACT Esters of organic monocarboxylic acids anddineoalkyl ethers with a tetrahydroxy functionality and corresponding tothe general structure wherein each R is an alkyl, aryl, or alkyarylgroup of one to 12 carbon atoms. These compounds are effective as highperformance functional fluids and lubricant base stocks over a widetemperature range.

6 Claims, N0 Drawings ESTERS OF TETRAHYDROXY DINEOALKYL ETHERSBACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to certain new esters of tetrahydroxy dineoalkyl ethers andtheir uses as lubricants and lubricant base stocks.

2. Description of Prior Art The continuing development and improvementof high performance aircraft engines has created a continual demand forimproved lubricants which are efficient over a wide range of operatingtemperatures and which are resistant to oxidation and thermaldegradation. Jet aircraft engines in particular are found to operatewith greater efficiency at higher temperatures, and consequentlyemphasis for jet engine lubricants has been on the high temperatureproperties.

The special requirements of the jet engines led to the development ofthe synthetic ester lubricants, the first commercial material beingdi-2-ethylhexyl sebacate. As more severe requirements and particularlyhigher and higher temperature requirements were placed upon thelubricants, technology advanced and produced the diesters, triesters,and finally polyesters formulated from hindered alcohols.

The hexaesters derived from dipentaerythritol have very good hightemperature properties and are widely used as lubricants in modern jetengines. The thermal stability and oxidation resistance of these estersare enhanced through the incorporation of additives such as amines,phenols, phosphites, etc., these additives being well known in the art.

Although emphasis is always directed toward the high temperatureproperties of the lubricants because these represent the normaloperating conditions, it is also important that the lubricant remainfluid at low temperatures in order that the lubricant can flow andperform its function when a cold engine is started. Ideally, thelubricant should have a sufficiently low pour point such that it can beused or stored at temperatures as low as F. The esters ofdipentaerythritol are generally deficient in this respect, and requirethe use of mixed esters and the addition of pour point depresants inorder to achieve the desired low temperature fluidity. The use of theseadditives represents additional cost for raw materials, handling andquality control. Consequently, the discovery of ester compositions whichhave the goodlubricity, thermal stability, and oxidation resistancecharacteristic of the dipentaerythritol esters, and in addition have superior low temperature properties, would be a major advancement in thestate of the high performance lubricant art.

SUMMARY OF THE INVENTION As a new composition, the esters of thisinvention are those derived from aliphatic or aromatic mono-carboxylicacids and dineoalkyl ethers having a tetrahydroxy functionality, saidesters corresponding to the general structure 2 wherein R, and Rindividually are alkyl groups of one to 12 carbon atoms or phenyl, and RR R and R, individually are alkyl, aryl, or alkylaryl groups of from oneto 12 carbon atoms.

These esters are excellent lubricants and lubricant base materialshaving exceptional lubricity, thermal stability, and oxidationresistance and having better low temperature properties than thecorresponding dipentaerythritol esters.

DESCRIPTION OF. PREFERRED EMBODIMENTS The dineoalkyl ethers'used in thepreparation of the novel esters of this invention are those compoundswhich contain four functional hydroxyl groups according to the followingstructural formula:

CHaOH CHrOH Rr- --CH3OCHr-C-Ra HrQH CHsOH wherein each R is an alkylgroup of from one to 12 carbon atoms or phenyl. Typical examples ofsuitable dineoalkyl ethers where R and R are lower alkyl groups aredi-trimethylolethane, di-trimethylolpropane, andtrimethylolethane/trimethylolpropane mixed ether. Examples ofcorresponding ethers'where R and R are higher molecular weight alkylgroups or phenyl include di-trimethylol butane, di-trimethylolpentane,di-trimethylolhexane, di-trimethylolheptane, di-trimethyloloctane,di-trimethylolhexane, etc., and mixed trimethylol alkane ethers. Anexample of the ether where R, and R are each phenyl isditrimethyloltoluene.

These tetrahydroxy dineoalkyl ethers are conveniently produced byreacting a neoalkoxide ion with a neoalkyl sulfonate to form a cyclicdineoalkyl ether intermediate then hydrolyzing said intermediate to formthe tetrahydroxy dineoalkyl ether. In a typical example, a trimethylolalkane is reacted with acetone to form a neoalkyl mono-o1 which in turnis reacted with metallic sodium to from a neoalkoxide ion. Additionalneoalkyl mono-o1 is reacted with toluene sulfonyl chloride to form aneoalkyl tosylate. The tosylate is then reacted with the neoalkoxide ionto form a cyclic dineoalkyl ether intermediate which is subsequentlyhydrolyzed to form the tetrahydroxy dineoalkyl ether.

The nomenclature used herein corresponds to that commonly employed fordi-polyols such as dipentaerythritol (di-PE). Specifically, the compoundis named according to the structure on either side of the oxyetherlinkage, with the oxyether linkage itself being counted as a hydroxylfor each side.

is di-pentaerythritol, two hydroxyls being replaced by the oxy-etherlinkage.

is named di-trimethylol propane, even though there are present on thecompound only four hydroxyls, two others being replaced by the oxyetherlinkage.

In order to obtain the novel esters of this invention, a dineoalkylether having the tetrahydroxy functionality as defined above is reactedwith an aromatic or aliphatic carboxylic acid or mixture of acids, suchas acetic, propionic, butyric, valeric, heptanoic, higher aliphaticacids, benzoic and other aromatic acids. The acids may be saturated orunsaturated, although the saturated lower aliphatic acids are generallypreferred for ester base lubricants. It is also to be understood thatthe acid anhydride or other acylating agents may be used as well as theacids themselves.

Illustrative of the novel esters of this invention are:di-trimethylolethane tetra-acetate, -propionate, -butyrate, -valerate,-pelargonate, -benzoate, -neoheptanoate, -cyclopentanecarboxylate, mixedbutyrate/benzoate, mixed valerate/isovalerate/decanoate, mixedbutyrate/valerate, etc; di-trimethylolpropane tetra-acetate, -butyrate,-valerate, -pelargonate, benzoate, mixed butyrate/valerate, etc;di-trimethyloltoluene tetra-acetate, -propionate, -butyrate, -valerate,etc; di-( 1,1 ,1-trimethylo1-2-ethylhexane) tetra-acetate, -butyrate,-valerate, mixed butyrate/propionate, benzoate, etc; di-( 1 l l-trimethyloldecane)tetraacetate, -propionate, -butyrate, -valerate,-benzoate, etc; trimethylol toluene/trimethylolethane ethertetraacetate, -propionate, -butyrate, -valerate, etc; trimethyloltoluene/trimethylolpropane ether tetraacetate, 'propionate, -butyrate,-valerate, mixed acetate/butyrate/valerate, etc; di-trimethylolbutanetetra-acetate, -propionate, -butyrate, -va.lerate,cyclopentanecarboxylate, -cyclohexanecarboxylate, mixedbutyrate/valerate, etc; ditrimethylol isobutane tetra-acetate,-propionate, -butyrate, -valerate, -mixed benzoate-propionate-valerate,etc.

The novel esters of this invention may be prepared by any of theconventional esterification methods which are well known in the art, themethod being not critical to the present invention. For example, thedineoalkyl polyol others may be esterified at temperatures between 60and 180 C., and in the presence of or absence of an inert solvent andesterification catalyst. The crude ester product may be purified byconventional procedures such as washing with alkali to remove excessacid and fractionation to remove volatile impurities.

The dineoalkyl esters of the present invention are useful as lubricants,hydraulic fluids, and other functional fluids for jet engines and inother areas which demand high performance over a wide temperature range.Many of the ester compositions included within the scope of thisinvention have serviceable viscosities at temperatures ranging from 40F. to 400 F. or higher. Some of the higher molecular weight compoundsare well suited for higher temperature service, such as above 600 F.

The esters of this invention are structurally and chemically related tothe dipentaerythritol esters, and may be used as alternativecompositions for most of the diPE uses. The esters of this invention aresuperior to the diPE esters in low temperature viscosity, and aretherefore preferred as lubricants and lubricant base stocks for lowtemperature applications. In this respect, the esters of this inventionrepresent an important advance in the state of the lubrication art.

The following examples are presented to illustrate the invention and todefine the properties of some of the novel esters included therein, butare not intended to be limiting of the scope of the present invention.

EXAMPLE 1 Preparation of di-trimethylolethane tetracetate A mixture of12.3 g. of di-trimethylolethane (di- TME) and 50 ml. of acetic anhydridewas heated slowly to C. at which point an exothermic reaction ensued.The solution was refluxed at C. for 10 min., then excess anhydride wasremoved by distillation. The residue was washed with water, dried, anddistilled to obtain 7.9 g. of the desired tetraacetate. b.p. l70-180Analysis: Calcd for C,,,H O C, 55.37; H, 7.75

Found: C, 54.97; H, 7.27

EXAMPLE [1 Preparation of di-trimethylolethane tetrabutyrate A mixtureof 47 g. of di-TME and g. of n-butyric anhydride was heated gradually toC. over a 4-hr. period. The excess anhydride was removed bydistillation. The residue was washed with water, dried, and distilled toyield 69.1 g. of the desired tetrabutyrate as a colorless oil; b.p.2lS-225 C/0.l mm., n 1.4,459,

Analysis: Calcd for C i-1 0 C, 62. 12; H, 9.23

Found: C, 62.06; H, 9.55

The following table illustrates the superior low temperature propertiespossessed by the di-TME esters of Examples 1 and 11 as compared to thecorresponding esters of dipentaerythritol (di-PE).

( l )Noncrystalline after storage at 40F. for several weeks.

EXAMPLE lll Preparation of di-trimethylolpropane tetravalerate A stirredsolution of 66.1 millimoles of ditrimethylolpropane, 33.7 g. of valericacid, 0.3 ml. of 85 percent phosphoric acid and 10 ml. of toluene washeated at 142 C. for 1% hours, and finally to 162 C. for 2 hours.Distillation gave the pure tetravalerate, b.p. 218216 C/0.1 mm., n1.4,516.

Analysis: Calcd for C H O C, 65.50; H, 9.96.

Found: C, 65.48; H, 9.78

EXAMPLE IV A series of esters based upon di-trimethylolethane (di-TME)and di-triemthylolpropane (di-TMP) were prepared from aliphatic andaromatic acids according to the procedure of Example 111 and evaluatedfor boiling point, density, and kinematic viscosity. The esters and theanalytical results are given in the Table below.

TABLE II Evaluation of Esters of the Formula pagoda omodn'li.(|)-C1I:OOH:(]JR

CIIQOICIIR 011105.11

Empbp Den- Kinematic Compound irical (F/ sity Viscosity (F.) R Formula760 (F.) 40 100 210 (1)C1-l Cl-l C H 0 663 1.1122 61.9 5.69

(2)CH C H, C I-1 0 745 1.0285 14,008 27.3 4.89

77) (3)Cl-l C 11 C H O 7161.0127 8,334 25.2 4.93

(4)0 11 CH C H O 701 1.0845 13 86.7 6.90

(100) )C H C 14 C ,,H O 738 1.0145 20,966 34.6 5.76

(100) (6)C H C 11 C I-1 ,0 802 1.0069 11.366 30.7 5.62

mcn c 11, c,,11,,o 718 1.0839 184 15.4

(100) (8)Cl-l C,H C H O 7951.1608 180 12.6

(100) (9)C1-l C H C l-1 ,0 7951.1608 79.4

( 1 )di-TME tetraacetate (2) di-TME tetrabutyrate (3 )di-TMEtetravalerate (4)di-TMP tetraacetate (5 )di-TMP tetrabutyrate (6)di-TMPtetravalerate (7)di-TME tetracyclopentanoate (8 )di TMEtetraneoheptanoate (9)di-TME tetrabenzoate EXAMPLEV A series of mixedesters based upon dib. cli-TME pentanoate/isopentanoate/decanoate mixedester Acid Ratio: pentanoic/isopentanonic/decanoic.

c. di-TME butyrate/valerate Acid Ratio: butyric/valeric.

d. di-TMP butyrate/valerate Acid Ratio: butyric/valeric.

b.p. Kinematic Viscosity of Ester F. 1760 mm Density (F.) -40 210 a 7551.0268 (100) 67x10 421 6.1 b 786 0.9746 (100) 13 1O 35.3 6.3 c 7361.0039 (100) 99x10 26.6 5.0 d 721 1.0054(100) 18 l0 34.8 2.1

Although the dineoalkyl esters of this invention are convenientlyprepared by esterification of the tetrahydroxy dineoalkyl ethers, thismethod of preparation is not limiting of the invention. For example, theesters may be formed directly from a precursor of the tetrahydroxy etherwhich has the following structural formula wherein each R is an alkylgroup of one to eight carbon atoms, and preferably is CH and R and R areindividually selected from the group consisting of alkyl groups of oneto 12 carbon atoms and phenyl. In this mode of preparation, the cyclicdineoalkyl ether defined above is first hydrolyzed to form the tetrol,then reacted with a selected monocarboxylic acid to form the ester insitu. The step of recovering the tetrol prior to reaction with the acidis thereby eliminated with a resulting savings in processing costs.

This mode of preparation is illustrated by the following example.

EXAMPLE VI Preparation of di-trimethylolethane tetravalerate A stirredmixture of 20 g. of di-trimethylolethane bisacetonide, 10 ml. of waterand 0.3 ml. of 85 percent phosphoric acid was heated to 62 C. for 5minutes to obtain a homogeneous solution. Then 33.7 g. of valeric acidwas added and the solution was heated to C. allowing overheaddistillation of volatiles. Toluene (10 ml.) was added and the solutionwas refluxed 1V2 hours with azeotropic removal of water, then finallyheated to 162 C. for 2 hours. Distillation yielded the puretetravalerate, IF 1.4,480.

Analysis: Calcd for C H O C, 64.48; H, 9.74.

Found: C, 64.77; H, 9.58.

The preceeding examples are directed to the esters and mixed esters ofthe di-TME and di-TMP ethers. However, it is to be understood that theseexamples are intended simply to illustrate the invention, and theinvention is not limited to the demonstrated examples. Otherdi-trimethylol alkyl and alkaryl ethers as described in thisspecification can also be employed in accordance with the teachingsherein, and therefore the invention is not to be limited except asdefined in the appended claims.

What I claim is:

1. An ester represented by the structure wherein R and R areindividually selected from the group consisting of alkyl radicals havingfrom one to 12 carbon atoms and phenyl, and R R R and R are individuallyalkyl radicals having from one to 12 carbon atoms.

2. An ester of claim 1 wherein R and R are individually selected fromthe group consisting of CH C H and C l-l

2. An ester of claim 1 wherein R1 and R2 are individually selected fromthe group consisting of CH3, C2H5, and C3H7.
 3. An ester of claim 1wherein R3, R4, R5 and R6 are residues of acids individually selectedfrom the group consisting of acetic, butyric, valeric, pelargonic, andneoheptanoic.
 4. An ester of claim 1 selected from the group consistingof a. di-trimethylolpropane tetraacetate, b. di-trimethylolpropanetetrabutyrate, c. di-trimethylolpropane tetravalerate, and d.di-trimethylolpropane tetraneohepanoate.
 5. An ester of claim 1 whereinR1 and R2 are CH3, and R3, R4, R5 and R6 are alkyl residues of acidsindividually selected from the group consisting of acetic, butyric,valeric, and neoheptanoic.
 6. Di-trimethylolethane tetravalerate.